ramda-groupby.ts

import R from "ramda";

type Person = {
  id: number;
  name: string;
  type: string;
};

function main() {
  const array: Person[] = [
    { id: 0, name: "_", type: "y" },
    { id: 1, name: "a", type: "x" },
    { id: 2, name: "b", type: "x" },
    { id: 3, name: "c", type: "y" },
    { id: 4, name: "d", type: "x" },
  ];

  const rejectByName = R.reject<Person, "array">(R.propEq("name", "_"));
  const groupByType = R.groupBy<Person>(R.prop("type"));    
  const composeFun = R.compose(groupByType, rejectByName);
    
  console.log(composeFun(array));
}

main();

Output:

{
 x: [
   { id: 1, name: 'a', type: 'x' },
   { id: 2, name: 'b', type: 'x' },
   { id: 4, name: 'd', type: 'x' }
 ],
 y: [ { id: 3, name: 'c', type: 'y' } ]
}